Sputnik 1

Sputnik 1 was the first artificial Earth satellite. It was a 585 mm (23 in) diameter shiny metal sphere, with four external radio antennae to broadcast radio pulses. The Soviet Union launched it into an elliptical low Earth orbit on 4 October 1957. It was visible all around the Earth and its radio pulses detectable. The surprise success precipitated the American Sputnik crisis, began the Space Age and triggered the Space Race, a part of the larger Cold War.